Human menopause is marked by an increase in serum cholesterol and triglycerides, and a reversal of the hdl/ldl ratio. Perhaps not coincidentally, post-menopausal women are at a significantly greater risk for coronary heart disease. While the occurrence of menopause has been documented in several nonhuman primate species, a change in the lipid and lipoprotein profiles of naturally post-menopausal nonhuman primates has not. The purpose of this study is to evaluate serum lipid and lipoprotein profiles as they relate to reproductive status in aged female rhesus macaques in order to further characterize the primate model for human menopause. The menstrual histories of 27 female rhesus macaques ages 20 years and older were retrospectively examined for 12 months previous to the initiation of the study. Each animal was categorized as either normomenorrheic (average cycle length >24 and <32 days), oligomenorrheic (average cycle length <24 or >32 days) or amenorrheic (no mensing in the last six months). Five females averaging 22.3 Years old were normomenorrheic, 14 females averaging 23.6 Years old were oligomenorrheic, and eight females averaging 24.1 Years old were amenorrheic. Daily urine samples were collected from these animals over a 12-week period from november 8, 1994 through measured via an in-house enzyme immunoassay. These assays will identify animals with abnormal luteal phases, and will be correlated with the animals' menstrual histories in order to most accurately identify post-menopausal animals. Monthly serum samples have been collected and serum lipid profiles are being run on each sample. These results will be correlated with the animal's reproductive status in order to determine if post-menopausal rhesus macaques experience the same increase in serum lipids and lipoproteins as post-menopausal women.